[zeromq-dev] Publish / Subscribe vs Multicast

gonzalo diethelm gdiethelm at dcv.cl
Mon Feb 15 22:03:49 CET 2010

I am answering some of my own questions here...

I have implemented a first version of the butterfly tutorial in ZMQ 2.0.
I am using ZMQ_UPSTREAM and ZMQ_DOWNSTREAM to connect all processes, and
it works fine, save for one thing: the load balancing. I am launching
two instances of component1 and two instances of component2 (in fact,
component1 and component2 now are identical, and only differ in their
command line parameters, but I digress).

I added as a command line parameter the name of the instance for each
component, and what I am seeing is that only the first instance launched
is receiving messages; the second instance never does anything.
Therefore, the overall throughput never changes.

More details:

1. send_requests does a bind to tcp:// (see step 5) and a
connect to tcp://
2. component1 does a bind to tcp:// and a connect to
3. zmq_streamer is configured thusly:
           <bind addr = "tcp://"/>
           <connect addr = "tcp://"/>
4. component2 does a bind to tcp:// and a connect to
5. receive_replies does a bind to tcp:// and a connect to
tcp:// (this last one is to send the final sync message).

Again, messages do flow but only through the first instances of
component1 and component2.

Do I have to do anything special in order to ensure that every process
that does a send to an endpoint, does it in a manner that it will be
load-balanced across all processes that are bound to that endpoint?

Gonzalo Diethelm

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